Method and apparatus for attaching refractory insulation to a support



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PATENT ATTORNEY Oct. 11, 1966 METHOD AND APPA FIG.

United States Patent O 3,277,872 METHOD AND APPARATUS FOR ATTACHING REFRACTORY INSULATION T A SUPPORT Paul Raymond Hoffmann and Lester M. Craig, Baton Rouge, La., assignors to Esso Research and Engineering Company, a corporation of Delaware Filed Feb. 3, 1965, Ser. No. 430,054 7 Claims. (Cl. 122-510) This invention relates to insulation mounting techniques in general and in particular to an improved method and apparatus for attaching refractory insulation material to a metallic supporting member operating within a high temperature furnace.

In furnaces of the type employed in the refining and cracking of hydrocarbons in the petroleum industry, it is customary to pass a petroleum vapor through a furnace in tubes which are subject to a high temperature radiant heat in the area of 2300 F. In supporting the Vaporcontaining groups of tubes in this process, a casting having a plurality of apertures extending therethrough for engaging the tubes is preferably employed. These metallic castings are in many instances subject to the direct high temperature radiation from the furnace burners and therefore may become softened and bent or at the very best deteriorate at a rate more rapid than the remaining components of the furnace. Accordingly it is highly desirable to protect the metallic tube supporting structure with a suitable refractory insulation similar to that employed in the remainder of the furnace walls.

In the past, this has been accomplished by securing a suitable refractory insulation material to the critical surface areas of the tube supports, particularly those areas with direct exposure to radiation from the heat source. In this way the temperature of the support is reduced and its life extended. However, in practice, difiiculty has been experienced in holding the protective refractory material to the tube supports due to the fact that differential thermal coeflicients of expansion exist between the metallic tube support and the refractory insulation.

The present invention provides a novel method and means for compensating for thermal stresses that normally occur between materials having different rates of thermal expansion in a furnace environment. In accordance therewith, a plurality of metallic studs are encircled with a collar or coring sleeve in an area adjacent the metallic supporting structure. Thereafter upon the firing of a plastic refractory metal applied over the studs and collars, a void area surrounding the length of the stud previously encircled by the combustible collar is created. In this way the mechanical securing means between the vitried refractory metal and the metallic supporting structure are provided with a relatively flexible unsupporting intermediate portion which permits differential growth rates between the components without fracture of the refractory insulation.

Accordingly, it is a principle object of this invention to provide an improved method and novel apparatus for securing a low coefficient of expansion refractory metal to a relatively high coefficient of expansion supporting structure.

A further object of the invention is to provide a novel means for attaching refractory insulation to a metallic surface.

A still further object of the invention is to provide a novel method of creating a void area around a portion of a refractory securing means employed in a petroleum cracking furnace.

These and other objects of the invention will become apparent and the invention will be fully understood from the following description and drawings in which:

3,277,872 Patented Uct. 1l, 1966 FIG. l is a side elevation view of a tube support in accordance with the invention with portions shown in section;

FIG. 2 is a side View of FIG. 1 with the refractory insulation metal omitted;

FIG. 3 is an enlarged detailed view showing a single attachment means and collar;

FIG. 4 is an enlarged cross-sectional View of the invention taken along line 4 4 of FIG. l; and

FIG. 5 is a perspective of the collar employed in the practice of the invention.

It will be understood that the drawings illustrate merely a preferred embodiment of the invention and that other embodiments are contemplated within the scope of the claims hereafter set forth.

Referring to the drawings in particular, a tube support 10 perferably made of a cast iron or steel of I cross section includes a pair of end plate portions 11 and a connecting web portion 13. The lower end of the tube support l@ is illustrated as being secured to a furnace oor designated 12 into which heat is directed from a suitable source 15 (see FIG. 4) to a petroleum vapor passing through a plurality of horizontally disposed tubes 16 passing through apertures 14 in the tube support. The exterior surfaces of the end plate portions 11 are preferably protected from direct radiation from the source 15 by a refractory insulating material 32. The refractory material 32 is attached to the support by a plurality of L-shaped studs 18 having their inner ends secured by welds 20 to plate 11. Each of the studs 18 includes a leg or shank portion 22 extending generally perpendicular to the plane of the plate portion 11 and an outer end portion extending in an upward direction generally parallel to the plate 11. The upper ends of the tube support 10 may be provided with suitable lugs 30 permitting engagement therewith of a similar tube support extending downwardly from an upper portion of the furnace (not shown).

Referring to FIG. 5, a sleeve or collar 24 is illustrated having a central aperture 26 sufiiciently large to permit the placement thereof over the stud 18. In one preferred method of construction, the stud 13 is butt welded to the surface of the plate 11. Thereafter the sleeve 24 is inserted over the stud and the stud is subsequently bent into the desired L shape. The refractory material 32 is commercially available in a plastic or clay-like consistency under the tradename Plibriko Super and is easily molded, rammed by hand, or otherwise applied over the studs 18 and the associated sleeves 24 into contact with the end plates 11. Thereafter during the initial heating of the furnace or during a preliminary firing process, the plastic refractory insulation is fired or vitrified to a hard and brittle consistency insulation material having a relatively low thermal coeicient of expansion relative to the coefficient of expansion of the supporting column 10. However the material of which the sleeve 24 is made is selected from a variety of materials which will vaporize, deteriorate, or otherwise disappear at the normal operating temperatures of the furnace so that a void area 24 is created in the space previously occupied by the sleeve during the application of the insulation in the plastic state. A cardboard collar has been found suitable, but those skilled in the art will readily appreciate that other materials such as wax may be substituted with equal success. In this way, once the refractory coated tube support attains its operating temperature, the L-shaped refractory securing studs 18 are unsupported at their inner portions in the area adjacent the plates 11. Because there is no general bond at the interface between the plate 11 and the insulation 32, the unsupported intermediate portions 22 of the studs 18 are free to flex to compensate for thermal stresses between the support and the insulation. It has been found that the use of the foregoing described novel method and apparatus has resulted in substantial increase in the life of the insulation material with a corresponding reduction in deteriorating effect of radiant heat upon the metallic support 10.

While a preferred specific embodiment of the invention has been shown and described in detail to illustrate the application of the inventive principles, it will be understood that the invention may be embodied otherwise without departing from such principles. i

What is claimed is:

1. The method of attaching a coating of refractory insulation having a first coefficient of thermal expansion to a supporting structure having a different coefiicient of thermal expansion and including elongated studs extending therefrom comprising the steps of encircling a portion of the length of said studs adjacent said supporting structure with a collar of combustible material, applying the refractory insulation material in a plastic state over said collars and studs, and heating said refractory material and supporting structure to a temperature sufficient to fire the refractory insulation material and vaporize the collar to produce a void area surrounding a portion of the length of said stud to permit flexing of said stud due to differential thermal expansion between said insulation and supporting structure.

2. The method of attaching a coating of refractory insulation to a supporting structure having a coefficient of thermal expansion different from that of the refractory insulation comprising the steps of securing one end of a plurality of irregularly-shaped studs to the surface of said supporting structure to receive said refractory insulation, placing sleeves of heat sensitive material about a portion of each of said studs adjacent said supporting structure to form a temporary core about a shank portion thereof, molding a plastic refractory insulation material over said studs and sleeves, and heating said refractory material to vitrify said material and at the same time to vaporize the sleeves for producing a void area surrounding a portion of the length of said studs to permit flexing of said studs due to differential thermal expansion between said vitrified insulation material and said supporting structure.

3. The method of attaching a coating of refractory insulation to a supporting structure having a coefiicient of thermal expansion different from that of the refractory insulation comprising the steps of securing one end of a plurality of irregularly-shaped studs in substantially perpendicular and predetermined spaced relationship to the surface of said supporting structure to receive said refractory insulation, placing sleeves of heat sensitive material about a portion of each of said studs adjacent said supporting structure to form a temporary core about a shank portion thereof, bending the unattached end portion of each of said studs into a generally parallel relationship with the surface of said supporting structure to thereby hold the sleeves thereon, molding a plastic refractory insulation material over said studs and sleeves, and heating said refractory material to vitrify it and at the same time to vaporize the sleeves for producing a void area surrounding a portion of the length of said studs to permit flexing of said studs due to differential thermal expansion between said vitrified insulation material and said supporting structur 4. A heat resistant tube support for use in a furnace comprising an elongated metal column having a generally I-shaped cross section, said column including a pair of generally parallel end plate portions and a connecting Web portion, said web portion having a plurality of spaced apertures for receiving and supporting tubes of diameter less than the diameter of said apertures extending therethrough, refractory insulation means disposed adjacent the exterior surface of said end plate portions for protecting said plate portions from direct radiation of heat within said furnace, said insulation means including a plurality of spaced recesses formed in the surface adjacent said end plate portions; and means for securing said insulation means to said end plate portions, said securing means comprising a plurality of spaced elongated stud means extending centrally through said spaced recesses having one end fixedly attached to said column and the opposite end embedded in said refractory material, whereby the central portion of said stud means is unsupported within said recess to permit bending thereof due to differential thermal expansion rates and temperatures between said metal column and said refractory insulation means.

5. A tube support in accordance with claim 4 wherein the embedded end of said stud means extends in a direction generally parallel to the plane of said plate portions.

6. Apparatus in accordance with claim 5 including lug means at one end of said column for engaging and attachment to a similar column.

7. A tube support for use in a furnace comprising first means of high mechanical strength and expansion coefficient for supporting the tubes to be heated in said furnace, second means of relatively low mechanical strength, expansion coeicient, and thermal conductivity for insulating said first means from direct radiant heat in said furnace, and flexible means for securing said second means to said first means for permitting differential thermal expansion therebetween, said flexible means including a plurality of elongated metallic studs, each of said studs having one end rigidly secured to said first means and its opposite end rigidly secured to said second means, said second means including a void portion surrounding an intermediate portion of each of said studs.

References Cited by the Examiner UNITED STATES PATENTS 1,972,593 9/1934 Keenan 122-6 2,841,122 7/1958 Tollow 122-6 3,050,813 8/1962 Kniveton 264-59 KENNETH W. SPRAGUE, Primary Examiner. 

7. A TUBE SUPPORT FOR USE IN A FURNACE COMPRISING FIRST MEANS FOR HIGH MECHANICAL STRENGTH AND EXPANSION COEFFICIENT FOR SUPPORTING THE TUBES TO BE HEATED IN SAID FURNACE, SECOND MEANS OF RELATIVELY LOW MECHANICAL STRENGTH, EXPANSION COEFFICIENT, AND THERMAL CONDUCTIVITY FOR INSULATING SAID FIRST MEANS FROM DIRECT RADIANT HEAT IN SAID FURNACE, AND FLEXIBLE MEANS FOR SECURING SAID SECOND MEANS TO SAID FIRST MEANS FOR PERMITTING DIFFERENTIAL THERMAL EXPANSION THEREBETWEEN, SAID FLEXIBLE MEANS INCLUDING A PLURALITY OF ELONGATED METALLIC STUDS, EACH OF SAID STUDS HAVING ONE END RIGIDLY SECURED TO SAID SECOND MEANS AND ITS OPPOSITE END RIGIDLY SECURED TO SAID SECOND MEANS, SAID SECOND MEANS INCLUDING A VOID PORTION SURROUNDING AN INTERMEDIATE PORTION OF EACH OF SAID STUDS. 